We will test the applicability of opponent-process theory to the development of morphine tolerance and the development of the morphine abstinence syndrome. These two developing phenomena will be studied as a function of dose size, dose duration and inter-dose interval. The critical decay duration of the opponent-process will be measured for each combination of variables and the data will be compared with analogous data on social attachment in ducklings. We will study the effects of naloxone on various types of tolerance to stressful UCSs. We will study the opponent-process in social attachment in chicks by using the presentation or removal of the UCS (imprinting object) to modulate tonic immobility in the domestic chick. We will continue our work on the effects of meal interruptions on total caloric intake in rats.